Multiwell assay/culture strip

ABSTRACT

A multiwell assay/culture strip provides an improved structure for a strip of wells as used for culturing cells and diagnostic testing, and comprises a strip or segment of generally identical well portions (typically eight or twelve wells) in linear arrangement adjacent one another and supported by a common base, and terminating in a first end and a second end. Each end bears a linking member extending perpendicularly from the end, and carries a receiver member conditioned to accept and frictionally engage an appropriate linking member of a separate strip. The linking members further provide offset basal surfaces to enhance stability of the strip.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to laboratory equipment andapparatus, and more specifically to an improved multiwell assay and/orculture strip.

2. Description of the Prior Art

Multiwell trays are typically made of molded plastic, such aspolystyrene, and have a number of generally identical well portionsarranged in a row and column array. Each well in the tray is analogousto a small test tube. Multiwell trays are generally intended assingle-use disposable items. A popular type of multiwell tray is themicroplate (also known as microtiter plates, micro-test plates, orsimply, plates). A microplate is about the size of a postcard and aboutone-half inch thick, with ninety-six wells arranged in an array of eightrows by twelve columns. Microplates are widely used for growing(culturing) living cells and in performing a variety of research anddiagnostic tests (assays) such as detection and identification ofantibodies, viruses, bacteria, drugs or other substances. It is a commonpractice to treat or coat the wells of a microplate with biologicalsubstances such as antigens or antibodies for use in particular assays.Various steps routinely performed in the course of culturing cells orperforming an assay can include inserting objects into the wells formixing or sampling the contents, filling the wells with liquid, emptyingthe liquid from the wells, and photometric reading which consists ofpassing a beam of light through the well and its contents to be measuredby a photosensitive detector.

As the use of microplates became more widespread, instruments weredeveloped to perform and automate various steps of the culturing andassay procedure. An ad hoc standard configuration for microplate andwell dimensions emerged as new manufacturers produced microplates ordeveloped equipment intended to be compatible or competitive with thosealready in existence.

As many different types of assays were developed (and are still beingdeveloped), it became clear that, in many cases, the standardninety-six-well microplate format represented an inconveniently largenumber of tests. To permit smaller numbers of tests to be performedconveniently, a number of manufacturers have produced modules or stripsof wells corresponding to only one row or column of wells on amicroplate. In keeping with the standard microplate configuration, thesemicrowell strips generally contain either eight or twelve wells. All ofthe presently available microwell strips require the use of arectangular retainer or frame member to hold the microwell strips. Theseframes have the same outside dimensions as the outer edge of atraditional microplate, and hold up to eight twelve-well strips or,alternatively, twelve eight-well strips. Therefore, a frame whencompletely filled with strips has the same dimensions and number ofwells as a microplate.

The frame performs several functions. It holds the strips upright andfacilitates handling since single strips usually tip over easily,spilling the well contents. The frame allows the user to assemble amicroplate-sized unit with between one to eight rows or between one totwelve columns of wells. Since the frame itself matches the outerdimensions of a microplate, it allows the use of these microwell stripswith certain microplate-compatible equipment. Each well in a strip isusually uniquely identified with a letter or number. Since the locationof a particular well may be important in specific cultures or assays,each frame generally includes some visual or mechanical mechanism sothat strips are uniformly aligned in the frame with their wells in thesame sequence.

There are some inherent disadvantages associated with use of the frame.It is a component which is not directly involved in the culturing ofcells or performance of the assay so its presence increases costs forproduction, packaging and handling. Use of a frame also increases theuser's handling requirement since strips must be manually placed withinthe frame or removed from it to get the desired number of wells. Also,because the maximum capacity of any frame is ninety-six wells (eighttwelve-well strips or twelve eight-well strips), multiple frames arerequired when more than ninety-six wells are desired. Also, although thestrips are intended as single-use disposable items, the frame canrepresent a potential source of contamination if used more than once.This risk may predominantly occur in commercially available test kits orother packaging configurations where one frame is typically suppliedwith a full complement of strips.

SUMMARY OF THE INVENTION

The multiwell assay/culture strip of this invention provides an improvedstructure for a strip of wells as used for culturing cells anddiagnostic testing. A preferred embodiment of the invention comprises astrip or segment of generally identical well portions (typically eightor twelve wells) in linear arrangement adjacent one another andsupported by a common base, and terminating in a first end and a secondend. The strip's first end bears a first tab or male linking memberextending perpendicularly from the first end, and carries a first slotor female receiver member conditioned to accept and frictionally engagea first male linking member of a separate strip. The strip second endanalogously bears a second tab or male linking member extendingperpendicularly from the second end, but in the opposite direction fromsaid first end male linking member, and carries a second slot or femalereceiver member conditioned to accept and frictionally engage a secondmale linking member of a separate strip. Thus, when a pair of separatestrips are brought together into parallel alignment with one another sothat the first nd male linking member of the initial strip is alignedwith the first end female receiving member of the separate strip, andthe second end male linking member of the initial strip is aligned withthe second end female receiving member of the separate strip, the twostrips may be connected by these respective, complementary connectors.

However, said first male linking member is specifically not engageablewith a second female receiving member of a separate strip, nor is saidsecond male linking member engageable with a first female receivingmember of a separate strip. Thus, separate strips can only be assembledin one fashion (first end to first end, and second end to second end).In situations where the sequence of wells is important, wells on alllinked strips will be similarly aligned. In addition, the visibledifferences between the first and second ends and their respective maleand female members (e.g., width, height, shape) provide the user with areadily visible means of alignment. 15 Any number of separate strips maybe linked together to assemble the desired size array of wells. Forexample, eight-well strips may be assembled to provide an array withsixteen, twenty-four, thirty-two, etc. wells, and twelve-well strips maybe assembled to provide an array with twenty-four, thirty-six,forty-eight, etc. wells. Furthermore, when twelve eight-well strips, oreight twelve-well strips are assembled, the rectangle defined by theedges of the strips and the projecting linking members has the same"footprint" as a standard ninety-six-well micro plate, thus renderingthe array suitable for standardized applications andmicroplate-compatible instruments, many of which use a carrier or holderwhere the microplate rests in a rectangular cut-out. Still further, anynumber of similar strips can be continuously assembled, rather thanbeing limited to multiples of the frame's capacity.

A given strip's linking members engage a separate strip's complementaryreceiving members in a horizontal plane (parallel to the bases). Thisfeature enables joinder and separation of separate strips upon ahorizontal plane, such as a flat working surface, which minimizes therisk of splashing or spilling the contents of the wells if the stripsmust be joined or separated while the wells are filled with liquid.

The perpendicularly-extending first and second male linking members eachinclude a lower surface which is coplanar with the strip base. Thus,these male linking members broaden the base of the strip beyond itsnormally linear contact with a working surface, and effectively preventthe strip from tipping over. This feature is important when the strip isused individually, without being assembled to a larger group of strips.

Thus, the present invention eliminates the need for a frame whilemaintaining all the advantages provided by the frame. The microplateconfiguration of present invention was developed to provide thefollowing functions equivalent to presently available microplate stripsand frames: stability against tipping for single strips; uniformalignment of wells in interlocked strips; and compatibility with"standard" microplate dimensions when eight twelve-well strips or twelveeight-well strips (ninety-six wells) are assembled.

The strip and tab design in the present invention also providesadditional benefits not found in present strips and frames: the spacerequired is defined by the desired number of strips rather than theframe; single strips which are filled with liquid can be handled,assembled and removed with minimal risk of spillage due to tipping orvertical engagement or removal in a frame; and any number of similarstrips can be continuously assembled rather than being limited tomultiples of the frame's capacity.

Other advantages associated with the elimination of a frame formultiwell strips are (a) reduction of production, packaging and handlingcosts both to the manufacturer and to the user, (b) increased speed andconvenience in handling and (c) no risk of contamination from reusing aframe. The present invention permits single or multiple strips withfilled wells to be removed and set aside for quality control or othertesting (filled single strips which require frames can easily tip andspill when not in their frames). The tabs on the present invention incombination with the ends of the strip give the same rectangular"footprint" as a standard microplate so that when assembled, eighttwelve-well strips or twelve eight-well strips can be used with mostexisting microplate-compatible equipment. However, the ability tocontinuously link large numbers of the present invention offerscompatibility with faster, simpler and less expensive equipment than ispresently required for handling strips in frames or for handlingindividual microplates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a series of multiwell assay/culturestrips of this invention, illustrating an independent strip as alignedfor engagement with a group of previously engaged strips;

FIG. 1A is a perspective view of a series of multiwell assay/culturestrips of this invention, as assembled into a ninety-six wellmicroplate;

FIG. 2 is a top plan view of a single multiwell assay/culture strip ofthis invention;

FIG. 3 is a partially cutaway side view of a single multiwellassay/culture strip of this invention;

FIG. 4 is a left end elevation view of a single multiwell assay/culturestrip of this invention, illustrating a first end male linking memberand female receiving member; and

FIG. 5 is a right end elevation view of a single multiwell assay/culturestrip of this invention, illustrating a second end male linking memberand female receiving member.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 is a perspective view of a series of multiwell assay/culturestrips of this invention, illustrating an independent strip as alignedfor engagement with a group of previously engaged strips. Strip 10comprises a plurality (here twelve) of wells 12 in linear, side-by-sidearrangement upon a base 14. Bridge portions 16 may connect therespective wells to provide added rigidity and strength. Strip 10includes a first end portion 20, bearing a tab or male linking member 22extending perpendicularly therefrom, and carrying a slot or femalereceiving member 24. Male linking member 22 is conditioned to engage acomplementary female receiving member 24a on a separate, adjacent strip10a. Strip 10a, as illustrated, is joined with adjacent strips 10b, 10cin like fashion.

Strip 10 also includes a second end portion 30, bearing a tab or malelinking member 32 extending perpendicularly therefrom and carrying aslot or female receiving member 24. Tab 32 extends in the oppositedirection from tab 22. As before, male linking member 32 is conditionedto engage a complementary female receiving member 34a on a separateadjacent strip 10a. However, male linking member 32 is specifically notengageable within female receiving member 24a, by virtue of itsnon-complementary geometry (e.g., it is too tall to fit within theopening of receiver member 24a). Similarly, male linking member 22 isspecifically not engageable within female receiver member 34 (e.g., itis too wide to fit within the opening of receiver member 34). Thislink-specific aspect prevents misalignment of the respective strips 10,10a, 10b, 10c.

FIG. 1A is a perspective view of eight twelve-well strips 10, 10a, 10b,10c, etc., as assembled into a ninety-six well microplate 11. Thiscombination yields the same rectangular "footprint" as a standard,unitary microplate, so that it can be used with most existingmicroplate-compatible equipment.

FIG. 2 is a top plan view of a single multiwell assay/culture strip ofthis invention. This view further 5 illustrates the visible dimorphismof the strip's first and second ends. Of course, the respective firstand second end's linking and receiving members could be of any practicalshape or size, so long as they achieve the desired link-specificcharacteristics.

FIG. 3 is a partially cutaway side view of a single multiwellassay/culture strip of this invention. This view illustrates therelatively flat bottom surfaces of first end male linking member 22 andsecond end male linking member 32. It is these flat bottom surfaces,extending perpendicularly in opposite directions some short distancefrom base 14, that extend the footprint of an individual strip's baseand provide it with additional stability.

This view also illustrates several desirable features of the wells andbase of the inventive strip. First, the wells are designed with flatbottoms which are level, uniform in thickness and coplanar with oneanother to provide uniformity for photometric reading of results inwhich a filtered light-beam passes vertically through the well tomeasure optical density of the contents. The corners of the wells areslightly radiused to permit easier flushing of the well's contents andreduce residual drops of liquid which tend to form more easily in rightangle corners. The depth and center-to-center spacing of the wells aresimilar to that of a standard microplate, achieving compatibility withexisting reading, washing, sampling, and dispensing equipment.Furthermore, with reference to the base 14, the interior of the baseincludes a recessed portion 15 extending the length of the stripimmediately beneath the aligned wells. This recessed area avoids contactwith the working surface, and thus avoids scratches which couldinterfere with the photometric reading of the wells. In addition, thecontour of this recessed area provides additional rigidity and strengthto the overall strip.

FIG. 4 is a left end elevation view of a single multiwell assay/culturestrip of this invention, illustrating a first end male linking memberand female receiving member, while FIG. 5 is a right end elevation viewillustrating a second end male linking member and female receivingmember. These views further illustrate the dimosphism of the respectivefirst and second ends, as well as the stabilizing base provided by thefirst and second male linking members 22, 32, respectively.

While this invention has been described in connection with preferredembodiments thereof, it is obvious that modifications and changestherein may be made by those skilled in the art to which it pertainswithout departing from the spirit and scope of the invention.Accordingly, the scope of this invention is to be limited only by theappended claims.

What is claimed as invention is:
 1. A multiwell assay/culture stripcomprising:a strip member having a base portion and a first and secondend; a plurality of well portions supported on said base portion inlinear, side-by-side arrangement; first male linking means located onsaid first end and extending some distance therefrom; first femalereceiver means located on said first end, said first female receivingmeans conditioned for releasable engagement with an identical first malelinking means of another strip member; second male linking means locatedon said second end and extending some distance therefrom; and secondfemale receiver means located on said second end, said second femalereceiving means conditioned for releasable engagement with an identicalsecond male linking means of another strip member; wherein said firstmale linking means are not engageable with said second female receivingmeans, and said second male linking means are not engageable with saidfirst female receiving means.
 2. The multiwell strip of claim 1 whereinsaid first male linking means extends perpendicularly in a firstdirection from said first end, and said second male linking meansextends perpendicularly in a second direction, opposite said firstdirection, from said second end.
 3. The multiwell strip of claim 2wherein said first and second male linking means each bears a bottomsurface, said bottom surfaces being coplanar with said strip base. 4.The multiwell strip of claim 3 wherein said base includes a recessedportion beneath said well portions.